Hardenable Steel Identification

[clm1899]

I got this 1” steel years ago and it still had some of the original wrapping which identified it. Well the wrapping is long gone and I can’t remember. Can it be identified by the green color or do I need to do some sort of quench testing to find out. Thanks

 

[RJSakowski]

My understanding is that their is no universal color coding standard. If you know the manufacturer, looking at their website might help. In my experience, the ends of the bar stock are usually what is color coded.

As to doing a spark test or a quench test, there are literally hundreds of different steels and other than telling you it has carbon content, there is little that you can do to identify the alloy.

 

[seasicksteve]

You can take it to a scrapyard and ask them to shoot it with an xrf to determine the chemistry. Once you have that you can determine the alloy. They may charge a few bucks if you find the right guy

 

[graham-xrf]

My understanding is that their is no universal color coding standard. If you know the manufacturer, looking at their website might help. In my experience, the ends of the bar stock are usually what is color coded.

As to doing a spark test or a quench test, there are literally hundreds of different steels and other than telling you it has carbon content, there is little that you can do to identify the alloy.

Various unrelated non-hobby circumstances have stalled my attempt to do this, but I do hope to get back to it. I have so much of the kit invested, and I got soooo close. I hesitate to even suggest @clm1899 check out the XRF thread. He should be warned!
BUT - there are a few first indicators to look for..

1. It has enough rust of a type that looks comparable to what is on the vise to the right of the picture. It is not among the chrom-moly air harden-able sorts. So not 4140.

2. Grind on it with something, and check out the old spark test. You already know it is not cast grey iron, or if not, try and drill it with a M3, see if it delivers the carbon powder. You should be able tell if it is cast semi-steel vs mild steel. Semi-steel makes sparks thinner that the big splashy non-hardenable mild steel, but still not quite like true cast iron. Take note of the nature of the sparks in a direct comparison to a lowly piece of old pipe, or angle iron that you already know is the mildest of squishy steel.

3. A chunk like that is unlikely to be the finest tool steel, but you can tell a bit by going ahead and messing with a strip from a little off-cut. Heat it up way too much, and quench. If it's hardenable, you will know. Sand or grind it along an edge, clean up shiny. Heat from one end, and stop and quench when the other end goes straw yellow brown. I know this is very approximate, but then try to scratch with a HS lathe tool. Some folk are pretty good at estimating the oxide thickness, and associating it with a temperature. There may even be a chart somewhere

4. You can try using a circular disc magnet, and attempting to compare the pull-away tug as compared to steels you already know.

My parting thought is that all of these are so unsatisfactory, and knowing what steel you have is of such major importance, it was always what bugged me. I agree totally with @seasicksteve 's suggestion that you should take a first shot by trying the scrapyard.

 

[RJSakowski]

Fifty three years ago when I took freshman chemistry, the way to identify materials was done through qualitative chemical analysis. This meant dissolving the sample in an appropriate solvent, usually something like aqua regia, and adding various chemical solutions to precipitate out product or create a distinctive color change. Typical metals, besides iron, alloyed in steels are manganese, chromium, nickel, cobalt, molybdenum, and a smattering of others. The definitive work on the subject was "Introduction to Semimicro Qualitative Analysis" by C. H. Sorum.

Beyond that, another analytical method was emission spectroscopy which would yield semi-quantitave results. It required a very expensive and huge spectrograph which created a plasma from the sample with an electric arc and analyzed the emitted spectrum via a photographic plate. Atomic absorption spectroscopy followed and was able to provide accurate compositions of metals. And the x-ray fluorescence spectroscopy mentioned by @graham-xrf is the latest in the arsenal.

The bottom line is that it is difficult, if not impossible, for a lay person to accurately identify a steel alloy. I realize this first hand as I have several tons of unknown steel alloys.

 

[benmychree]

I would start by cutting off a small sample and first try to harden it by quenching in oil, then if it does not significantly harden, re heat it and try quenching in water, if it does not harden in water, it would likely be low carbon steel. Common steels may be O-1, W-! and 4140 or just plain mild steel, the fact that it was paper wrapped suggests that it could be a tool steel.

 

[ChazzC]

I would start by cutting off a small sample and first try to harden it by quenching in oil, then if it does not significantly harden, re heat it and try quenching in water, if it does not harden in water, it would likely be low carbon steel. Common steels may be O-1, W-! and 4140 or just plain mild steel, the fact that it was paper wrapped suggests that it could be a tool steel.

Precision ground low carbon (A36) flat bar stock comes wrapped in paper.

 

[benmychree]

Precision ground low carbon (A36) flat bar stock comes wrapped in paper.

Yes, very true, but many other tool steels are also wrapped in paper, it proves nothing.

 

[durableoreo]

Sorry to be annoying but the difficulty of identifying steels is a good reason for labeling. I mark both ends and several places along the stock with sharpie. I've used p-Touch stickers with some success, too. Engrave or somehow mark your stock. It's the cheapest and easiest (and only) solution to the problem.

With that said, for steels, the most important thing is the carbon content. So do a spark test and compare to mild steel and a known tool steel. See the wikipedia page---it details various components by spark color. Harden a coupon if you're not sure.

Distinguishing between alloys with oil or water quenching seems difficult. The idea of oil quenching steels is that they take a good quench despite the heat being drawn out more slowly than with water. A fast quench can cause cracks in some parts. You'd need to develop a test coupon that cracks almost 100% of the time in water hardening steels first... Still, it might be a useful test.

 

[durableoreo]

The definitive work on the subject was "Introduction to Semimicro Qualitative Analysis" by C. H. Sorum.

I've been curious about this for a long time. There's a bunch of cheap copies of this book on Amazon, so I ordered one. The newest edition is 117 $ but used was about 5 $ including shipping.